MVHR design, already have the supply and extract air flow rates, what's next?

[irnbru]

Hello everyone! I am currently in a university final year project, where I am responsible for the design of the MVHR system. I am completely new to this, and I have been stuck in this for quite a while. I already have the extract and supply air flow rates, what should be next? Should I start sizing the ducts (deciding there radii)? Or is there any other thing I should do? 

[JohnMo]

Not wanting to do your project for you, but point you in directions where you can research.  You need to build an index of topics you need to cover to justify MVHR, steps to design, choices for the design and implementation, costs 'v' cost savings etc.

 

You will need to know each circuit pressure drop, what noise suppression you need and MVHR unit size you would select, what features the unit will incorporate and if boost will be automated or manual, reasons why any cost and/or user implications.  If automated on humidity, what downsides there are in a UK climate and high summer time humidity and how to overcome. If manual what is a user never boosts what impacts on the building fabric.

 

Also look at the UK implications of low internal humidity resulting from MVHR in the winter.  Is this an issue in the UK or is it more a cold climate thing.

 

Look at the Passivhaus Institute, building regulations, for the country where your house is sited.  There is also plenty of information on this site.

 

You should also demonstrate how your flow rates compare to house volume and overall air changes per hour.  Comparing building regs with something like Passivhaus guidelines.

 

Advantage/diadvantages of various system configurations dMVHR, MVHR and hybrids between the two such as Fresh-R.  Again look at costs, ease of implementation of new build and retrofit.

[irnbru]

16 hours ago, JohnMo said:

Not wanting to do your project for you, but point you in directions where you can research.  You need to build an index of topics you need to cover to justify MVHR, steps to design, choices for the design and implementation, costs 'v' cost savings etc.

 

You will need to know each circuit pressure drop, what noise suppression you need and MVHR unit size you would select, what features the unit will incorporate and if boost will be automated or manual, reasons why any cost and/or user implications.  If automated on humidity, what downsides there are in a UK climate and high summer time humidity and how to overcome. If manual what is a user never boosts what impacts on the building fabric.

 

Also look at the UK implications of low internal humidity resulting from MVHR in the winter.  Is this an issue in the UK or is it more a cold climate thing.

 

Look at the Passivhaus Institute, building regulations, for the country where your house is sited.  There is also plenty of information on this site.

 

You should also demonstrate how your flow rates compare to house volume and overall air changes per hour.  Comparing building regs with something like Passivhaus guidelines.

 

Advantage/diadvantages of various system configurations dMVHR, MVHR and hybrids between the two such as Fresh-R.  Again look at costs, ease of implementation of new build and retrofit.

Thank you so much!

[Adrian Walker]

1 hour ago, irnbru said:

Thank you so much!

BTW what course are you studying?

[Roundtuit]

If you haven't already, spend some time on the websites of mvhr suppliers (eg BPC) and see what kit is commercially easily available; there's a lot of useful info out there.  Ducting comes in standard sizes, so you only need to establish whether you need 1 run or 2 to each vent.

[irnbru]

13 hours ago, Adrian Walker said:

BTW what course are you studying?

mechanical engineering

[irnbru]

6 hours ago, Roundtuit said:

If you haven't already, spend some time on the websites of mvhr suppliers (eg BPC) and see what kit is commercially easily available; there's a lot of useful info out there.  Ducting comes in standard sizes, so you only need to establish whether you need 1 run or 2 to each vent.

Sorry...I'm really new to this. What do you mean 1 run or 2 to each vent?

[Roundtuit]

I can only speak with reference to my install, but one size of ducting is used throughout.  Most rooms have a single run of duct from the manifold to either a supply or extract vent  but in bigger (or wetter) rooms with a greater feed or extract requirement, two runs of ducting are used to get enough air flow.  Adjustable vents are then used to throttle-back the flow at each outlet to balance the system.

[irnbru]

3 minutes ago, Roundtuit said:

I can only speak with reference to my install, but one size of ducting is used throughout.  Most rooms have a single run of duct from the manifold to either a supply or extract vent  but in bigger (or wetter) rooms with a greater feed or extract requirement, two runs of ducting are used to get enough air flow.  Adjustable vents are then used to throttle-back the flow at each outlet to balance the system.

oh I didn't know such thing existed, thank you! I think for my project, one run should be enough. 

[Roundtuit]

7 minutes ago, irnbru said:

oh I didn't know such thing existed, thank you! I think for my project, one run should be enough. 

Looks like the kitchen needs twice the extract that the small bathroom needs, but I'm sure you'll be doing the maths! 

[dpmiller]

Definitely take some time to peruse supplier websites. Heck, get them to do a design for you that you can then reverse-engineer to understand the process...